The present invention relates to a shaft and sleeve assembly structure to be used, for example, in automatic transmissions of automobiles.
Conventionally, in this type of shaft and sleeve assembly structure to be used in automatic transmissions of automobiles, as shown in FIG. 6, a shaft 62 is inserted into a sleeve 61, and a needle roller bearing 63 is fitted between the shaft 62 and the sleeve 61.
In this structure, an axial hole 65 bored axially from an end portion 62A of the shaft 62 is formed, and a radial through hole 66 radially extending through from a specified axial position of the axial hole 65 is bored. Then, working oil is supplied to the needle roller bearing 63 through the axial hole 65 and the radial through hole 66. For this supply, the axial hole 65 and the radial through hole 66 serve as an oil passage, and a seal ring 67 is fitted between the end portion 62A of the shaft 62 and the sleeve 61 so that the working oil does not flow between the end portion 62A of the shaft 62 and the sleeve 61. This seal ring 67 is a rubber member made of urethane rubber or the like.
However, the prior art structure as described above has a problem that when the shaft 62 is inserted inside the needle roller bearing 63, the seal ring 67 fitted to the shaft end portion 62A tends to strike against an axial end portion 73A of a cage 73 as shown in FIG. 5A, making the seal ring 67 damage. There is a further problem that the seal ring 67 tends to catch on an inner end 72A of a flange portion 72 bent radially inward of an outer ring 71, making the seal ring 67 damaged.
Furthermore, when the end portion 73A of the cage 73 is bent radially outward so as to be hidden behind the outer ring flange portion 72 as shown in FIG. 5B so that the seal ring 67 does not strike against the end portion 73A of the cage 73, there is a problem that the seal ring 67 may enter into between the outer ring flange portion 72 and an end face 75A of a roller 75, making the seal ring 67 damaged.
In addition, if the diameter of the shaft end portion 62A is made smaller than the diameter of a shaft central portion 62B as shown in FIG. 4, then the seal ring 67 can be prevented from striking against the needle roller bearing 63 to some extent. However, too small a diameter of the end portion 62A would cause the structure to lack strength.